The overall objective of this proposed research is to increase our fundamental understanding of the interaction of high intensity laser radiation with dental hard tissues and apply that knowledge to the development of laser based methods that selectively remove dental caries and composite restorative materials using an integrated approach of computer-controlled laser beam scanning coupled with optical methods of feedback. In addition to eliminating the noise and vibration associated with the dental hand-piece, lasers offer several unique advantages over current surgical technology for conservative dentistry. Under the appropriate irradiation conditions, lasers are capable of achieving markedly higher precision and selectivity, are well-suited for electronic control, can induce beneficial chemical and morphological changes in the walls of the drilled cavity that can render the tissues more resistant to further dental decay with enhanced adhesive properties to restorative materials. The specific aims of this proposal are to test the following hypotheses: 1) that caries lesions can be safely and selectively removed from tooth surfaces at clinically relevant rates using image guided laser ablation, and 2) that composite can be safely and selectively removed from tooth surfaces at clinically relevant rates using laser ablation in conjunction with spectral feedback. These fundamental studies will significantly advance our overall knowledge of laser-tissue interactions and facilitate the development of safer and more efficient laser systems for the removal of dental caries and restorative materials. The use of highly selective laser systems for the removal of dental caries and dental composites is likely to lead to the practice of more conservative dental procedures that will reduce the amount of healthy tissue loss that is generally associated with conventional cavity preparations and the repair of existing composite restorations.